chore(deps): update dependency sinon to v15 (#433)

Co-authored-by: Jeff Ching <chingor@google.com>

Author: renovate-bot

action/package-lock.json

@@ -39,7 +39,7 @@
     "gts": "^3.1.1",
     "js-yaml": "^4.1.0",
     "mocha": "^10.1.0",
-    "sinon": "^14.0.2",
+    "sinon": "^15.0.0",
     "ts-jest": "^29.0.3",
     "typescript": "^4.8.4"
   }

action/package.json

@@ -64,7 +64,7 @@
     "nock": "^13.0.2",
     "null-loader": "^4.0.0",
     "pack-n-play": "^1.0.0-2",
-    "sinon": "^14.0.0",
+    "sinon": "^15.0.0",
     "ts-loader": "^8.0.0",
     "typescript": "^4.6.4",
     "webpack": "^5.0.0",